Current transformer CT secondary open circuit solution
Principle of current transformer CT secondary overvoltage protector to prevent the secondary open circuit of current transformer CT
1 The loop instrument indicates an anomaly, which is generally reduced or zero. The open circuit of the current loop used to measure the meter will cause the three-phase ammeter indication to be inconsistent, the power meter indication to be reduced, and the meter speed to be slow or no rotation. If the meter indicates sometimes no, it may be in a semi-open state (poor contact).
2 The CT body of the current transformer has no noise, uneven vibration, serious heating, smoking and other phenomena, of course, these phenomena are not obvious in load hours
3 Current transformer CT secondary circuit terminal, component wire head discharge, ignition phenomenon.
4 Relay failure or failure to operate, which can be detected and dealt with in case of failure or tripping.
5 kilowatt-hour meters, relays, etc. smoke and burn out. The reactive power meter and the watt-hour meter, the transmitter of the remote device, and the relay of the protection device are burned out, which will not only make the CT secondary open circuit, but also make the PT secondary short circuit.
Conclusion and Troubleshooting:
The above are some basic clues to check the CT secondary open circuit. In fact, in normal operation, the primary load is not large, the secondary no work, and the current circuit is not open for measurement, the fault of the CT secondary open circuit is not easy to find. To check and deal with the secondary open circuit fault of CT, it is necessary to minimize the primary load current to reduce the voltage of the secondary circuit. Pay attention to safety when operating, stand on the insulation mat, wear insulation gloves, and use well-insulated tools.
(1) When CT secondary open circuit is found, it is necessary to distinguish which group of current circuit faults, the difference of the open circuit, whether it has an impact on protection, report scheduling, and remove the protection that may be misoperated.
(2) Minimize the primary load current. If the CT is seriously damaged, the load should be transferred and the power should be cut off. The principle of current transformer CT secondary overvoltage protector is introduced to prevent CT secondary open circuit
(3) Try to short-circuit CT twice on the nearest test terminal with a good short wire according to the drawing as soon as possible, and then check the processing open point.
(4) If there is a spark found when shorting, then the shorting should be effective, and the fault point should be in the circuit below the short contact, which can be further found. If there is no spark when short-circuiting, the short-circuiting may be invalid, the fault point may be in the circuit before the short contact, and the short contact can be transformed forward point by point to narrow the scope of inspection.
(5) Within the fault range, terminals and components that are prone to failure should be checked. For checked faults that can be handled by themselves, such as loose external components such as wiring terminals, poor contact, etc., immediately deal with them and put them into the withdrawn protection. If the open point is on the terminal of the current transformer model body, the power should be cut off. If it can not be handled by itself (such as inside the relay) or can not identify the fault by itself, the CT should be reported to the superior after a second short circuit.